Cloudflare security features cause site to flicker/flash during rendering

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I can’t find any posts that are similar to what I am experiencing. This is happening on our domain

We decided to move our caching to Edgio CDN, but we like Cloudflare DNS, DDoS and WAF, so we are trying to use both CDNs. We set our Cloudflare cache to bypass.

To demonstrate the issue, I have two URLs. The first one uses a Cloudflare proxy that redirects to the Edgio proxy. The second one only has an Edgio proxy. Both URLs use the exact same Origin Server. All pages have this issue, but I chose this page because it is a simple SSR page (pulled from Edgio cache), yet the Cloudflare URL appears to be triggering a full client-side re-rendering of the cached page.

What are the steps to reproduce the error:
If you Inspect both of these URLS with slow 3G throttling, you will see that the Cloudflare proxied URL displays a blank white page around the 15 to 20 second mark of the page rendering. The Edgio proxied URL does not do this. With the slow 3G throttling, you see the issue as a blank white page, whereas is you use a faster connection, the issue is just an annoying flicker/flash during page rendering.

Another interesting fact.

  1. The Cloudflare proxied URL performs 84 server requests.
  2. The Edgio proxied URL performs only 58 server requests. Is Cloudflare adding an additional 26 files to each page request?

What steps have you taken to resolve the issue?

  1. We also tried turning off the Cloudflare proxy, while still using the Cloudflare URL. This gave us similar results to the Edgio proxied URL.
  2. We set the Cloudflare Cache to Bypass.

Have you tried from another browser and/or incognito mode?
Yes. It does the same thing in Edge, Chrome and incognito more.

Turn off Polish. It is a feature specifically related to low bandwidth connections to improve LCP.

1 Like

@cscharff thanks for the suggestion. I turned off Polish, but the issue is persisting. I am still experiencing the UI flashing while the page renders while using the Cloudflare proxy.